A disadvantage with Open Delta is there are no phase-ground voltage measurements, which is only a disadvantage if directional relaying or distance relaying is needed. Some directional and voltage based ground fault detection relays don't work without the phase to ground input. Since most industrial systems MV are high resistance grounded and ground fault protection is provided by overcurrent, there isn't a need for the phase-ground measurements.
Why will the directional or distance relaying not work in this case?
5. Most directional and distance relays need a voltage to ground reference to compare with the phase current nfr groudn faults. Some can use a zero sequence polarising current from CT's on the neutral of the transformer, but most need phase-neutral voltages for accurate calculation of fault direction and distance.
The relay needs to see a zero sequence voltage to compare to the zero sequence current to find out which direction the current is flowing.
Precise Phase-ground voltages are needed for this type of calculation, whether it is done digitally or with analog circuits or windings, coils and phae shifting circuits.
The voltages provided by the Open Delta do not have enough zero sequence component.
yes open all fuses close the primary neutral tap,remove secondary leads off of bad traansformer,tell customer to reduce his load until bad transformer can be replced.
yes
The open Delta or V-Connection transformer is an improvement of the 1 three-phase transformer. The open Delta transformer can restore power in a Delta-Delta three-phase bank when one of the three single-phase transformers, which can be individually disconnected and replaced in case of failure, breaks down. The open Delta transformer then allows functionality to be restored, but at a reduced power of 57.7 of the original power.
There are various ways in which you can connect a three-phase transformer's primary and secondary windings, or in which you can connect three single-phase transformers to create a three-phase transformer bank. For example: wye-wye, wye-delta, delta-delta, delta-wye, etc.For each connection, there is a natural phase shift between the primary and secondary line voltages. This is called the angular displacement (or 'phase displacement') of the transformer connection.If you wish to parallel two three-phase transformers, or two three-phase transformer banks, then their angular displacements must be the same (there are also other requirements not relevant to this answer).A vector group is a method of specifying a three-phase transformer (or transformer bank) method of connection and its angular displacement. Transformer connections from the same group can be paralleled. Those in different groups cannot
Yes, you can use three single phase transformers on three phase applications and interconnect them to serve as a single transformer or you could use one single phase transformer fed from two of the three lines in a step down application.
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yes open all fuses close the primary neutral tap,remove secondary leads off of bad traansformer,tell customer to reduce his load until bad transformer can be replced.
yes
The open Delta or V-Connection transformer is an improvement of the 1 three-phase transformer. The open Delta transformer can restore power in a Delta-Delta three-phase bank when one of the three single-phase transformers, which can be individually disconnected and replaced in case of failure, breaks down. The open Delta transformer then allows functionality to be restored, but at a reduced power of 57.7 of the original power.
There are various ways in which you can connect a three-phase transformer's primary and secondary windings, or in which you can connect three single-phase transformers to create a three-phase transformer bank. For example: wye-wye, wye-delta, delta-delta, delta-wye, etc.For each connection, there is a natural phase shift between the primary and secondary line voltages. This is called the angular displacement (or 'phase displacement') of the transformer connection.If you wish to parallel two three-phase transformers, or two three-phase transformer banks, then their angular displacements must be the same (there are also other requirements not relevant to this answer).A vector group is a method of specifying a three-phase transformer (or transformer bank) method of connection and its angular displacement. Transformer connections from the same group can be paralleled. Those in different groups cannot
An open-delta connection is a method of providing a three-phase supply, using two single-phase transformers. It is particularly useful if , say, one single-phase transformer, part of a three single-phase transformers forming a three-phase transformer bank, becomes damaged -allowing the two remaining transformers to provide a temporary three-phase supply to the load. The drawback with this connection is that the capacity of the transformer bank is reduced, and it can only provide a lower load current.
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The main advantage is that the 'footprint' of a three-phase transformer is smaller than a transformer bank, and all connections are prewired which makes them easier and quicker to install and replace.
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The function of the radiator ban in a transformer is to cool the transformer oil.